Metal-to-insulator transition in La_1−xBa_xTiO₃

Abstract

The ferroelectric insulator BaTiO₃ can be electron-doped by substitution of divalent Ba²⁺ with trivalent La³⁺ , creating d states at the transition-metal sites. The successive filling of the 3 d Ti band initiates a sequence of electronic transitions. First, the system undergoes an Anderson-type insulator-to-metal-transition into a paramagnetic and metallic state, and second, a correlation-induced antiferromagnetic and insulating phase is established for La-rich concentrations. Ceramic La_1−xBa_xTiO₃ samples covering the whole concentration range were systematically examined utilizing measurements of resistivity, specific heat, and magnetic susceptibility in the temperature range 1.8 < T < 300 K . The concentration dependence of the Sommerfeld coefficient γ and the Pauli spin susceptibility was systematically investigated. The temperature dependence of the resistivity was studied in detail. In addition a ( T , x ) phase diagram of La_1−xBa_xTiO₃ was constructed.